Question

An amorphous solid A burns in air to form a gas B which turns lime water milky. The gas is also produced as a by-product during the roasting of sulphide ore. This gas decolourises acidified aqueous \[KMn{O_4}\] solution and reduces \[F{e^{3 + }}\] to \[F{e^{2 + }}\]. Identify the solid A and the gas B.

Answer 1

Hint: Here, in this question, we have to identify the amorphous solid A and gas B. An amorphous solid is one in which the constituent particles do not follow a typical three-dimensional path.

Complete Step by Step Solution:
Amorphous solids are similar to liquids in that they lack an organised structure, such as a three-dimensional plan of atoms or ions. The solid to liquid transformation occurs over a wide temperature range since these substances do not have a sharp dissolving point. Amorphous solids' physical properties are generally isotropic, meaning they don't depend on the direction of estimation and show the same extent in all directions.
Since Gas B is obtained as a by-product during roasting of sulphide, the gas must be sulphur dioxide. The chemical reaction is as follows:
\[2ZnS + 3{O_{_2}}\xrightarrow{{}}2ZnO + 2S{O_2}\]
From the above reaction, gas B is sulphur dioxide.
Gas B decolourises \[KMn{O_4}\] the solution. The reaction is as follows:
\[2KMn{O_4} + 5S{O_2} + 2{H_2}O\xrightarrow{{}}2{K_2}S{O_4} + 2MnS{O_4} + 2{H_2}S{O_4}\]
In the above reaction, \[KMn{O_4}\]is in violet colour. It is converted into \[{K_2}S{O_4}\] which is colourless.
Gas B reduces \[F{e^{3 + }}\] to \[F{e^{2 + }}\]. The reaction is as follows:
\[F{e_2}{\left( {S{O_4}} \right)_3} + S{O_2} + 2{H_2}O\xrightarrow{{}}2FeS{O_4} + 2{H_2}S{O_4}\]
In the above reaction, \[F{e_2}{\left( {S{O_4}} \right)_3}\] has iron in \[F{e^{3 + }}\]state and it is converted into \[FeS{O_4}\] has iron in \[F{e^{2 + }}\] the state.
The above reactions confirm that gas B is sulphur dioxide.
The gas B is obtained when an amorphous solid A burns in the air. We know that gas B is sulphur dioxide. It is produced when sulphur (\[{S_8}\]) burns in the air. The reaction is as follows:
\[{S_8} + 8{O_2}\xrightarrow{{}}8S{O_2}\]
From the above reaction, amorphous solid A is sulphur (\[{S_8}\]).
Therefore, Amorphous solid A is sulphur (\[{S_8}\]) and gas B is sulphur dioxide (\[S{O_2}\]).

Note: Because of their unique characteristics, amorphous solids have a wide range of uses. Inorganic glasses, for example, are used in buildings, houseware, and research facilities. Rubber, another amorphous solid, is used to make tyres, tubes, and shoe bottoms, among other things. Plastics are widely used in both households and industries.